Early-age creep behavior of concrete-filled steel tubular members subjected to axial compression

In concrete-filled steel tubular (CFST) structures, the loading age of the concrete core is usually earlier than that of other concrete structures, resulting in early-age creep. Early-age creep has significant influences on stress redistribution within the cross-section, and also on the deformation, of the CFST structures. Experiments were conducted to investigate the early-age behaviors of compressive CFST members. The CFST specimens were loaded at ages of 1, 3, 7, and 28d to acquire the creep growth at different loading ages. Meanwhile, the elastic moduli of concrete at corresponding ages were tested. Moreover, stress transfer between the concrete core and outer steel tube during the creep was analyzed using a modified fib Model Code 2010 (MC2010) creep model. The findings illustrate that a dynamic process exists in stress redistribution within cross-sections of the CFSTs at early ages, and increase of the stress on the concrete core due to elastic modulus development will counteract decrease of the stress on the concrete core due to the creep. (C) 2020 Elsevier Ltd. All rights reserved.